The present invention is a divisional application of the patent application Ser. No. 11/311,085 filed on Dec. 20, 2005, entitled “Multi-range cross defrosting heat pump system and humidity control system.”
In general, current heat pump system has very limited range of working temperatures due to the limitation and the operation efficiency of the compressor; however, in many circumstances, the environment temperature may vary from negative 40 degree to 20 degree Celsius, therefore it is main objective of the present invention to provide a multi-range cross defrosting heat pump capable of operating under a wide range of working environment temperature at high efficiency.